Carcinogens human

Since 1979 the use of 24 5 T has been regu lated in the United States It is likely that the United States Environmental Protection Agency will classify some dioxins as known and others as probable human carcinogens and recommend further controls be placed on processes that produce them It appears from decreasing dioxin levels in some soils that exist mg regulations are having some effect ... 

Formaldehyde is classified as a probable human carcinogen by the International Agency for Research on Cancer (lARC) and as a suspected human carcinogen by the American Conference of Governmental Industrial Hygienists (ACGIH). This is based on limited human evidence and on sufficient evidence in experimental animals (136). Lifetime inhalation studies with rodents have shown nasal cancer at formaldehyde concentrations that overwhelmed cellular defense mechanisms, ie, 6 to 15 ppm. No nasal cancer was seen at 2 ppm or lower levels (137). 

Health nd Safety Factors. Isophorone is considered moderately toxic by ingestion and skin contact. Some rat tumor formation evidence has been found (264), but no demonstration as a human carcinogen has been proven. Isophorone is considered an Environmental Protection Agency (EPA) priority pollutant, and has a permissible acute toxicity concentration of 117, 000 ///L to protect freshwater aquatic life, 12, 900 ///L to protect saltwater aquatic life, and 5, 200 ///L to protect human life (265). Isophorone is mildly toxic by inhalation, but because of its low volatiUty it is not a serious vapor hazard. 

C using a dehydration catalyst consisting of alurninosihcate, Al O, or siUca gel (45). 1-Naphthaleneamine is also toxic (LD q (dogs) = 400 mg/kg) and a suspected human carcinogen, which conditions mandate that appropriate precautions be followed in manufacture and use. 

It is very difficult to treat MDA as a single entity because the manufacturing processes of PMDA and MDA are essentially identical, with the exception of a separation step. This article focuses on the technology of 4,4 -MDA, and it also includes properties of isomers and oligomeric mixtures when they are of commercial importance. The 4,4 -MDA is a suspected human carcinogen, and therefore special handling of this material is required. AH of the MDA and PMDA produced is consumed in industries that are "destmctive" of MDA s chemical identity. Thus MDA loses its unique chemical identity and is not encountered by household consumers. 

Nitrosamines. Findings that secondary amines, so common in mbber accelerators, can react with NO species to form the suspected human carcinogens, nitrosamines, have prompted active programs to develop alternative accelerators. Neither primary nor tertiary amines form stable nitrosamines and they are generally considered to be safe materials. The abiHty of each type of common mbber accelerator class to form nitrosamines has been summarized and depends on their 1°, 2°, or 3° nature (30). 

Ethylene dibromide is a suspected human carcinogen and worker exposure by all routes should be carefiiUy controUed to levels as low as reasonably achievable (67). Ethylene dibromide causes severe blistering of the skin if contact is prolonged. Eye contact with the Hquid will cause pain, irritation, and temporary impairment of vision. Recommended safety equipment includes safety goggles, a NIOSH approved canister-type gas mask for organic vapors, neoprene gloves, and neoprene overshoes. In case of contact with ethylene dibromide, contaminated clothing and shoes should be removed and eyes or skin washed with plenty of water for at least 15 minutes. Contaminated clothes should be washed before reuse and contaminated shoes should be discarded. 

A. Barter and R. S. Nair, Review of the S cientific Evidence on the Human Carcinogenic Potential ofPara-Dichloroben iene, Chlorobenzene Producers Association, Washington, D.C., 1990. 

Recommendations by the ACGIH are classified as threshold limit values (TLV) based on 8-h TWA. Chromium metal and alloys, Cr(II) compounds and Cr(III) compounds, including chromite ore, have a TLV of 0.5 mg/m Cr in air. Water-soluble Cr(VI) compounds have a TLV of 0.05 mg/m Cr. Certain water-insoluble Cr(VI) compounds, ie, the chromates of 2inc, barium, calcium, lead, strontium, sintered chromic acid, and processing chromite ores, also have a TLV of 0.05 mg/m as well as a human carcinogen designation (145). 

Health and Safety. Eree phenols may be present in phenoHc novolacs and resoles. Phenol [108-95-2] is poisonous and caustic, irritating the skin and mucous membranes. Eormaldehyde and ammonia [7764-41-7] are often emitted during the cure of novolacs and must be properly vented. Eormaldehyde is Hsted as a human carcinogen worker exposure and emissions are controUed by OSHA and the EPA. 

Sulfur Compounds. Ethylene thiourea [96-45-7] a suspected human carcinogen, is prepared by reaction of carbon disulfide [75-15-0] CS[) in aqueous EDA (47). 

OSHA considers that, at excessive levels, ethylene oxide may present reproductive, mutagenic, genotoxic, neurologic, and sensitization hazards. In addition, ethylene oxide is considered by OSHA, lARC, and NTP as a potential human carcinogen. 

The formation of nitrosamines, e.g. n-nitrosodiedianolamine, which are possible human carcinogens, can occur in synthetic or semi-synthetic fluids which contain a nitrite salt and diethanolamine or triethanolamine. 

Suspected human carcinogens - see TLV Appendix A, Category A2 (below). 

A1 - Confirmed Human Carcinogens. Substances, or substances associated with industrial process, recognized to have carcinogenic potential. 

A2 - Suspected human carcinogens. Chemical substances, or substances associated with industrial process, which are suspect of inducing cancer, based on their limited epidemiological evidence or demonstration of carcinogenesis in one or more animal species by appropriate methods. 

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